Flip chip integration on qubit chips

Abstract

A quantum bit (qubit) flip chip assembly may be formed when a qubit it formed on a first chip and an optically transmissive path is formed on a second chip. The two chips may be bonded using solder bumps. The optically transmissive path may provide optical access to the qubit on the first chip.

What is claimed is: 
     
       1. A method for forming a quantum bit (qubit) flip-chip assembly, the method comprising:
 forming a qubit on a first chip; 
 forming an optically transmissive path in a second chip; and 
 bonding the first chip to the second chip; and 
 wherein the optically transmissive path is located above the qubit. 
 
     
     
       2. The method of  claim 1 , wherein the path has an aperture with a diameter large enough to allow for treatment of the qubit. 
     
     
       3. The method of  claim 1 , wherein the optically transmissive path has an aperture of 100 microns or less. 
     
     
       4. The method of  claim 1 , further comprising laser annealing the qubit by applying a laser through a surface of the qubit chip that is opposite the second chip. 
     
     
       5. The method of  claim 1 , further comprising ion etching the qubit. 
     
     
       6. The method of  claim 1 , wherein the forming the optically transmissive path comprises drilling, using a high-power laser beam, the second chip to form a through-hole in the second chip. 
     
     
       7. The method of  claim 6 , wherein the etching comprises deep-reactive ion etching. 
     
     
       8. The method of  claim 6 , wherein the etching comprises a chemical etch, and wherein the chemical etch is a tetramethylammonium hydroxide (TMAH) etch. 
     
     
       9. The method of  claim 1 , wherein the forming the optically transmissive path comprises etching a through-hole in the second chip. 
     
     
       10. The method of  claim 1 , wherein the second chip comprises a transparent substrate. 
     
     
       11. The method of  claim 10 , wherein the transparent substrate is Magnesiumoxide (MgO). 
     
     
       12. A flip chip apparatus comprising:
 a first chip comprising a qubit; 
 a second chip bonded to the first chip, wherein the first chip and the second chip are bonded by a plurality of solder bumps; and 
 wherein an optically transmissive path in the second chip provides for optical access to the qubit on the first chip. 
 
     
     
       13. The apparatus of  claim 12 , wherein the second chip comprises a transparent substrate. 
     
     
       14. The apparatus of  claim 13 , wherein the transparent substrate is sapphire. 
     
     
       15. The apparatus of  claim 12 , wherein the optically transmissive path has a diameter large enough to allow for treatment of one or more of the plurality of qubits. 
     
     
       16. The apparatus of  claim 12 , wherein the qubit is accessible for laser annealing via the optically transmissive path. 
     
     
       17. The apparatus of  claim 12 , wherein the optically transmissive path of the second chip is aligned with the qubit on the first chip. 
     
     
       18. The apparatus of  claim 12 , wherein the optically transmissive path is formed with a chemical etch. 
     
     
       19. The apparatus of  claim 12 , wherein the optically transmissive path is formed using a high-power laser beam. 
     
     
       20. The apparatus of  claim 12 , wherein the first chip is comprised of a transparent substrate.